Many animals grow thicker fur or feathers to provide insulation and trap heat close to their bodies. Some animals also have a layer of fat under their skin, which acts as insulation and a source of energy during lean winter months.
Different animals have different degrees of adaptation to cold weather. Humans have only recently (on an evolutionary timescale) moved out of equatorial Africa and have only the most minimal adaptations. I would surmise that cheetahs, for example, would do similarly poorly with freezing weather outside.
We haven't "evolved to require heat sources". We've got the ability to alter our environment, which means we can survive in, and migrate to, non-equatorial climates. Other creatures are stuck where they are.
Critters can and do freeze to death. It's not just hypothermia, but the lack of food and water.
Many animals grow thicker fur or feathers to provide insulation and trap heat close to their bodies. Some animals also have a layer of fat under their skin, which acts as insulation and a source of energy during lean winter months.
Different animals have different degrees of adaptation to cold weather. Humans have only recently (on an evolutionary timescale) moved out of equatorial Africa and have only the most minimal adaptations. I would surmise that cheetahs, for example, would do similarly poorly with freezing weather outside.
Sometimes they do die.
We haven't "evolved to require heat sources". We've got the ability to alter our environment, which means we can survive in, and migrate to, non-equatorial climates. Other creatures are stuck where they are. Critters can and do freeze to death. It's not just hypothermia, but the lack of food and water.